Users are people with registered accounts. You can register on: https://tanlet.classyedu.eu/register (or by clicking Registration on the upper right corner of the login screen) by entering a username, a password, an email address and a preferred language (you can change the language of the screens anytime at the upper right corner). After registration the users can be invited to groups or they can subscribe to public groups, from where they can access the contents of the group.